JP2023002074A - Misfire detection device for internal combustion engine - Google Patents

Abstract

To provide a misfire detection device for an internal combustion engine, which can calculate a torsional velocity component with high accuracy.SOLUTION: A CPU substitutes a difference between a crank-side speed ωe, which is the rotation speed of a crankshaft, and a rear stage-side speed ωout, which is a speed of a damper on the side opposite to the crankshaft, into a differential speed ωdamp (S46). The CPU calculates a torsion angle θdamp by integration processing of the differential speed ωdamp (S48). The CPU calculates a torsional velocity component ωr, which is the velocity component of the crankshaft due to torsion of the damper, on the basis of multiplication of the torsion angle θdamp and a damper stiffness value K (S58). Based on the torsional speed component ωr, the CPU calculates a time T30 as a variable representing the speed of the crankshaft (S60), which is used for misfire determination. The CPU switches the value of the damper stiffness value K depending on whether or not a vehicle is idling (S50-S54).SELECTED DRAWING: Figure 3

Description

The present invention relates to a misfire detection device for an internal combustion engine.

For example, Patent Literature 1 listed below describes a misfire detection device applied to an internal combustion engine in which a crankshaft is mechanically connected to a drive wheel side via a damper. This device is based on a physical model that inputs the difference between the rotational speed of the crankshaft and the rear-stage speed, which is the rotational speed of the drive wheel side of the damper, and calculates the torsional speed due to resonance of the rotational speed of the crankshaft. Calculate the components. In this device, the presence or absence of misfire is determined based on a value obtained by removing the torsional speed component from the rotation speed of the crankshaft.

The above physical model is a model using the fact that a value obtained by multiplying the torsion angle of the damper by the damper stiffness value becomes the torque applied to the damper. Here, the integrated value of the difference indicates the twist angle of the damper. Therefore, the torque applied to the damper can be calculated by multiplying the integrated value by the damper stiffness value. Since this torque determines the rate of change of the torsional angle, the torsional rate component can be calculated based on this torque.

JP 2008-248877 A

By the way, since the relationship between the torsion angle and the torque applied to the damper fluctuates, if the damper rigidity value is fixed, it may not be possible to accurately express the target characteristics by the physical model.

Means for solving the above problems and their effects will be described below.
Applied to an internal combustion engine having a plurality of cylinders, the crankshaft of the internal combustion engine is connected to a torsionally rigid body, crank side acquisition processing, post-stage acquisition processing, torsional speed component calculation processing, and determination fluctuation amount calculation and determination processing, wherein the crank-side acquisition processing is processing for acquiring a crank-side speed variable, which is a variable indicating the rotation speed of the crankshaft, based on the crank signal, and the latter-stage acquisition processing includes: This is a process of obtaining a rear-stage speed variable, which is a variable indicating the rotational speed of the torsional rigid body on the side opposite to the crankshaft, and the torsional speed component calculation process includes the crank-side speed variable and the rear-stage speed variable. A process of calculating a torsional velocity component, which is a velocity component caused by the torsion of the torsional rigid body, based on the damper stiffness value using the difference of the velocity variables as an input, the process including a stiffness value changing process, and calculating the variation amount for determination. The process is a process of calculating a determination variation amount based on the value of the crank-side speed variable from which the torsional speed component is removed, and the determination variation amount indicates the rotation variation amount used for misfire determination. the amount of rotation fluctuation is the amount of change in the crank-side speed variable; the determination processing is processing for determining whether or not there is a misfire in the internal combustion engine based on the magnitude of the variation for determination; The stiffness value varying process is a misfire detection device for an internal combustion engine, which is a process of changing the damper stiffness value based on the magnitude of the load on the internal combustion engine.

The relationship between the torsion angle of the damper rigid body and the torque has nonlinearity. On the other hand, when the load on the internal combustion engine is large, the torque applied to the internal combustion engine is large compared to when the load is small, so the center of fluctuation of the torsion angle tends to deviate from zero. If the center of fluctuation deviates from zero, the angle that the misfire detection device recognizes as the torsion angle of zero may deviate from the actual zero point. Therefore, if the same constant of proportionality is used as the damper stiffness value when the load is large and when the load is small, the physics specification of the torsionally rigid body cannot be accurately represented by the physics model. Therefore, in the above configuration, by changing the damper stiffness value based on the magnitude of the load on the internal combustion engine, the physical characteristics of the torsionally rigid body can be expressed with high accuracy regardless of the magnitude of the load on the internal combustion engine. Therefore, with the above configuration, the torsional velocity component can be calculated with high accuracy, so misfire can be detected with high accuracy.

The figure which shows the control apparatus and drive system concerning one Embodiment. FIG. 4 is a flowchart showing the procedure of processing executed by the control device according to the embodiment; FIG. FIG. 4 is a flowchart showing the procedure of processing executed by the control device according to the embodiment; FIG. The figure which shows the relationship between the damper torsion angle and torque concerning the same embodiment. Sectional drawing which shows the structure of some dampers. (a) and (b) are sectional views showing the state of the coil spring of the damper. (a) and (b) are diagrams showing the tendency of a map for calculating a damper stiffness value.

An embodiment will be described below with reference to the drawings.
As shown in FIG. 1, the internal combustion engine 10 is a four-stroke engine having four cylinders #1, #2, #3 and #4. A crankshaft 12 of the internal combustion engine 10 is coupled with a crankrotor 20 provided with teeth 22 . The toothed portion 22 indicates each of a plurality of rotation angles of the crankshaft 12 . The crank rotor 20 is basically provided with teeth 22 at intervals of 10° CA, but there is one missing tooth portion 24 where the interval between adjacent teeth 22 is 30° CA. is provided. This is for indicating the reference rotation angle of the crankshaft 12 .

A planetary gear mechanism 30 that constitutes a power split device is mechanically connected to the crankshaft 12 via a damper 14 . The damper 14 has a coil spring and exhibits elastic force. Planetary gear mechanism 30 divides the power of internal combustion engine 10 , first motor generator 40 , and second motor generator 50 . A crankshaft 12 is mechanically connected to the carrier C of the planetary gear mechanism 30 via a damper 14 . A rotation shaft 42 of a first motor generator 40 is mechanically connected to the sun gear S of the planetary gear mechanism 30 . A rotating shaft 52 of the second motor generator 50 is mechanically connected to the ring gear R of the planetary gear mechanism 30 . The output voltage of the first inverter 44 is applied to the terminals of the first motor generator 40 . Also, the output voltage of the second inverter 54 is applied to the terminals of the second motor generator 50 .

Ring gear R of planetary gear mechanism 30 is mechanically coupled to drive wheel 34 via transmission 32 in addition to rotating shaft 52 of second motor generator 50 .
The control device 60 operates various operation units of the internal combustion engine 10 in order to control the torque, the exhaust component ratio, etc., which are the control amounts of the internal combustion engine 10 as the controlled object. Further, the control device 60 operates the first inverter 44 in order to control the torque, rotation speed, etc., which are the control amounts of the first motor generator 40 as a controlled object. In addition, the control device 60 operates the second inverter 54 in order to control the torque, rotation speed, etc., which are the control amounts of the second motor generator 50 as a controlled object.

The control device 60 refers to the output signal Scr of the crank angle sensor 70 when controlling the control amount. Control device 60 also refers to output signal Sm1 of first rotation angle sensor 72 that detects the rotation angle of rotation shaft 42 of first motor generator 40 . Control device 60 also refers to output signal Sm2 of second rotation angle sensor 74 that detects the rotation angle of rotation shaft 52 of second motor generator 50 .

The control device 60 has a CPU 62 , a ROM 64 , a RAM 66 and peripheral circuits 68 , which can communicate with each other via a local network 69 . Here, the peripheral circuit 68 includes a circuit that generates a clock signal that defines internal operations, a power supply circuit, a reset circuit, and the like. The control device 60 controls the control amount by causing the CPU 62 to execute programs stored in the ROM 64 .

FIG. 2 shows the procedure of processing executed by the control device 60 . The processing shown in FIG. 2 is implemented by the CPU 62 repeatedly executing a program stored in the ROM 64 at a predetermined crank angle cycle. Note that, hereinafter, the step number of each process is represented by a number prefixed with “S”.

In the series of processes shown in FIG. 2, the CPU 62 first acquires the time T30 required for the crankshaft 12 to rotate 30° CA (S10). Next, the CPU 62 sets “m=0, 1, 2, 3, . (S12). These processes are processes for increasing the numbers of the variables in parentheses after the time T30 in the past. By these processes, when the value of the variable in parenthesis is one larger, the time T30 is 30°CA earlier.

Next, the CPU 62 determines whether or not the current rotation angle of the crankshaft 12 is ATDC 120°CA with reference to the compression top dead center of any one of the cylinders #1 to #4 (S14). When the CPU 62 determines that the ATDC is 120° CA (S14: YES), the CPU 62 substitutes the rotation fluctuation amount ΔT30[m] for the rotation fluctuation amount ΔT30[m+1], and subtracts the time T30[4] from the time T30[0]. The obtained value is substituted for the rotational fluctuation amount ΔT30[0] (S16). The rotation fluctuation amount ΔT30 is a variable that takes a negative value when a misfire does not occur in the cylinder whose misfire is to be determined, and a positive value when a misfire occurs. Here, the cylinder subject to the presence/absence of misfire is the cylinder determined to have passed the compression top dead center by 120° in the process of S14.

Next, the CPU 62 determines whether or not the value obtained by subtracting the rotation fluctuation amount ΔT30 "2" from the rotation fluctuation amount ΔT30[0] is equal to or greater than the threshold value ΔTth (S18).
This process is a process of determining whether or not a misfire has occurred in a cylinder to be determined. That is, when no misfire has occurred, the rotational fluctuation amount ΔT30[0] and the rotational fluctuation amount ΔT30[2] are approximately the same value, so the absolute value of the difference between them is small. On the other hand, when a misfire occurs in the cylinder targeted for determination, the rotation fluctuation amount ΔT30[0] becomes a positive value. On the other hand, if no misfire has occurred in the cylinder that reached compression top dead center 360° CA before the cylinder to be determined, the rotation fluctuation amount ΔT30[2] becomes a negative value. Therefore, when a misfire occurs in the cylinder to be determined, the value obtained by subtracting the rotation fluctuation amount ΔT30 "2" from the rotation fluctuation amount ΔT30[0] is a positive value with a large absolute value.

If the CPU 62 determines that it is equal to or greater than the threshold value ΔTth (S18: YES), it makes a provisional determination that a misfire has occurred (S20). Then, the CPU 62 increments a counter Cn that counts the number of provisional determinations (S22).

The CPU 62 determines whether or not a predetermined period of time has elapsed when the process of S22 is completed and when the process of S18 makes a negative determination (S24). Here, the starting point of the predetermined period is the later timing of the timing when the process of S18 is executed for the first time and the timing when the process of S32, which will be described later, is finally executed. When determining that the predetermined period has elapsed (S24: YES), the CPU 62 determines whether or not the counter Cn is equal to or greater than the threshold value Cth (S26). The threshold Cth is set according to the lower limit of the misfire rate when misfire occurs at a misfire rate that cannot be overlooked within a predetermined period. That is, the length of the predetermined period and the threshold value Cth are predetermined according to the lower limit value.

When the CPU 62 determines that it is equal to or greater than the threshold value Cth (S26: YES), it makes a final determination that a misfire has occurred (S28). Then, the CPU 62 operates the warning light 80 shown in FIG. 1 to execute notification processing for notifying the user that the misfire rate has occurred at a level that cannot be overlooked (S30). On the other hand, when determining that the counter Cn is less than the threshold value Cth (S26: NO), the CPU 62 initializes the counter Cn (S32).

It should be noted that the CPU 62 temporarily terminates the series of processes shown in FIG. 2 when the processes of S30 and S32 are completed and when a negative determination is made in the processes of S14 and S24.
FIG. 3 shows the procedure of processing for calculating the time T30 required for the crankshaft 12 to rotate 30° CA. The processing shown in FIG. 3 is implemented by the CPU 62 repeatedly executing a program stored in the ROM 64 at a cycle in which the crankshaft 12 rotates 30° CA. Specifically, for example, the detection of a predetermined tooth portion 22 by crank angle sensor 70 is used as a trigger to repeatedly execute. It should be noted that the predetermined tooth portion 22 is defined every 30° CA.

In the series of processes shown in FIG. 3, the CPU 62 first calculates the time et3txdh required for the crankshaft 12 to rotate through the most recent rotation angle range of 30°CA (S40). As shown in FIG. 1, this process is a process of measuring the time required for the crank angle sensor 70 to detect either one of the two teeth 22 separated by 30° CA until it detects the other. . Next, the CPU 62 divides the angular constant CR corresponding to 30°CA by the time et3txdh to calculate the crank-side speed ωe, which is the rotational speed of the crankshaft 12 in the most recent 30°CA rotation angle range (S42 ).

Next, the CPU 62 calculates the post-stage speed ωout, which is the rotational speed of the carrier C side of the damper 14 (S44). The CPU 62 determines the post-stage speed ωout based on the rotation speed ωm1 of the rotation shaft 42 of the first motor generator 40 in the small rotation angle region and the rotation speed ωm2 of the rotation shaft 52 of the second motor generator 50 in the small rotation angle region. Calculate At this time, the CPU 62 refers to the gear ratio of the planetary gear mechanism 30 . Here, the minute rotation angle region is defined as a rotation angle region smaller than one rotation. Further, the rotation speed ωm1 is calculated by the CPU 62 based on the output signal Sm1 of the first rotation angle sensor 72 . Further, the rotation speed ωm2 is calculated by the CPU 62 based on the output signal Sm2 of the second rotation angle sensor 74 .

Next, the CPU 62 substitutes a value obtained by subtracting the downstream speed ωout from the crank speed ωe into the differential speed ωdamp (S46). Next, the CPU 62 calculates the twist angle θdamp between the crankshaft 12 side of the damper 14 and the carrier C side based on the process of integrating the differential speed ωdamp (S48). Here, the CPU 62 regards the average value of the twist angle θdamp in a predetermined period as the point where the twist angle θdamp is zero in order to suppress the accumulation of errors due to the integration process. Broadly speaking, this can be realized by, for example, the following three processes. The first process is a process of calculating a new torsion angle θdamp by integrating the differential velocity ωdamp per unit section. The second process is a process of updating the average value based on the torsion angle θdamp newly calculated this time. A third process is a process of setting a value obtained by subtracting the updated average value from the newly calculated torsion angle θdamp as the final torsion angle θdamp.

Next, the CPU 62 determines whether or not the internal combustion engine 10 is idling (S50). Here, idling is defined as an operation in which the shaft torque of the internal combustion engine 10 is controlled to be zero. In other words, the operating state is such that the rotational speed of the crankshaft 12 of the internal combustion engine 10 is maintained only by the combustion control of the internal combustion engine 10 .

When the CPU 62 determines that the vehicle is not idling (S50: NO), the CPU 62 performs map calculation of the damper stiffness value K using normal map data (S52). On the other hand, if the CPU 62 determines that the vehicle is idling (S50: YES), the CPU 62 performs map calculation of the damper stiffness value K using the idle map data (S54).

Here, the reason for switching the damper stiffness value depending on whether it is idling will be described.
FIG. 4 shows the relationship between the torsional angle θdamp of the damper 14 and the torsional torque Tdamp that is the torque generated in the damper 14 . As shown in FIG. 4, the relationship between the torsion angle θdamp and the torsion torque Tdamp has nonlinearity. Specifically, when the torsion angle θdamp changes from zero to positive, the set torque T1 is abruptly applied. Further, when the torsion angle θdamp switches from zero to negative, a set torque “(−1)·T1” is abruptly applied. The set torque is a torque generated due to the spring provided in the damper 14 being provided in a compressed state even when the torsion angle θdamp is zero.

FIG. 5 shows a cross-sectional configuration of part of the damper 14. As shown in FIG. As shown in FIG. 5, both ends of the coil spring 14a are sandwiched between sheets 14b. FIG. 5 shows the case where the twist angle θdamp is zero. The length L1 of the coil spring in this case is shorter than the free length L0 at which the elastic force is zero.

Returning to FIG. 4, in the damper 14, the amount of change in the torsional torque Tdamp with respect to the amount of change in the torsional angle θdamp changes greatly depending on whether the magnitude of the torsional angle θdamp is smaller or larger than the threshold value θth. This is due to the difference in how the load of the coil spring 14a is applied to the seat 14b depending on the magnitude of the torsion angle θdamp.

FIG. 6(a) shows a cross section of part of the damper 14 when the twist angle θdamp is less than the threshold θth. As shown in FIG. 6A, in this case, the inner peripheral side of the coil spring 14a applies a load to the seat 14b, while the outer peripheral side of the coil spring 14a does not apply a load to the seat 14b.

FIG. 6(b) shows a cross section of part of the damper 14 when the twist angle θdamp is greater than the threshold θth. As shown in FIG. 6B, in this case, both the inner peripheral side and the outer peripheral side of the coil spring 14a apply a load to the seat 14b. Therefore, when the torsion angle θdamp exceeds the threshold θth, the torque changes with respect to the change in the torsion angle θdamp more than when the torsion angle θdamp is less than the threshold θth.

As described above, the CPU 62 regards the average value of the twist angles θdamp as the zero point of the twist angles θdamp. However, when the axial torque of the internal combustion engine 10 continues to be greater than zero, the twist angle θdamp recognized by the CPU 62 differs from the actual zero point shown in FIG. Therefore, if the damper stiffness value K is set based on the characteristics shown in FIG. not.

Based on the above, the ROM 64 stores normal map data and idle map data.
FIG. 7(a) shows the relationship between the absolute value of the torsion angle θdamp and the damper stiffness value K indicated by the idle map data. As shown in FIG. 7A, when the absolute value of the torsion angle θdamp is equal to or less than the backlash width θ0, the damper stiffness value K is zero. This indicates the angular range in which the damper 14 can rotate without twisting the damper 14 even when the crankshaft 12 rotates due to the mechanical backlash of the planetary gear mechanism 30 . This is because the torsion angle θdamp is not an actual torsion angle of the damper 14 but a calculated torsion angle. Incidentally, FIG. 4 shows the relationship between the actual twist angle θdamp and the torque.

In the range of the torsional angle θdamp from the backlash width θ0 to the set width θ1, the set torque causes the damper stiffness value to increase rapidly. Then, when the set width θ1 is exceeded, the damper stiffness value K becomes a substantially constant value. Note that the idle map data may include data of a portion where the absolute value of the twist angle θdamp exceeds the threshold θth. In that case, the damper stiffness value should be rapidly increased when the twist angle θdamp exceeds the threshold value θth.

FIG. 7B shows the relationship between the absolute value of the torsion angle θdamp and the damper stiffness value K indicated by the normal map data. As shown in FIG. 7B, the damper stiffness value K is substantially constant regardless of the absolute value of the twist angle θdamp. This setting is based on the assumption that the actual value of the torsion angle θdamp is greater than the threshold θth during non-idle operation. Note that the normal map data may be data in which the damper stiffness value K increases when the torsion angle θdamp is extremely large. As a result, if the change in torsional torque Tdamp with respect to the torsional angle θdamp is larger than the inclination shown in FIG.

When completing the processes of S52 and S54, the CPU 62 substitutes the value obtained by multiplying the torsion angle θdamp by the damper stiffness value K for the torsion torque Tdamp (S56 in FIG. 3).
Then, the CPU 62 calculates a torsional speed component ωr, which is a speed component obtained by quantifying the influence of the torque generated by the torsion of the damper 14 on the rotational speed of the crankshaft 12, based on the process of integrating the torsional torque Tdamp (S58). . Here, a physical model is used in which the torsional velocity component ωr is calculated by integrating angular acceleration components of the crankshaft 12 proportional to the torsional torque Tdamp. Then, the CPU 62 substitutes the value obtained by dividing the angle constant CR by the value obtained by subtracting the torsional speed component ωr from the crank-side speed ωe for the time T30 (S60).

When completing the process of S60, the CPU 62 once terminates the series of processes shown in FIG.
Here, the action and effect of this embodiment will be described.

The CPU 62 performs misfire detection processing using a time T30 obtained by dividing the angular constant CR by a value obtained by subtracting the torsional speed component ωr from the crank-side speed ωe. Here, the CPU 62 uses the damper stiffness value K in calculating the torsional velocity component ωr. Then, the CPU 62 sets the damper stiffness value K to different values depending on whether the internal combustion engine 10 is idling. Thereby, the torsional torque Tdamp can be calculated with high accuracy.

According to the present embodiment described above, the actions and effects described below can be obtained.
(1) The CPU 62 sets the damper stiffness value K to zero when the absolute value of the torsion angle θdamp is equal to or less than the backlash width θ0. As a result, it is possible to represent a region in which the torsion angle θdamp does not increase due to the mechanical backlash of the power transmission system connected to the crankshaft 12 regardless of the rotation of the crankshaft 12 .

(2) The CPU 62 abruptly increases the damper stiffness value K in a region where the absolute value of the torsion angle θdamp is equal to or greater than the backlash width θ0 and equal to or less than the set width θ1. Thereby, the set torque of the damper 14 can be expressed.

<Correspondence relationship>
Correspondence relationships between the items in the above embodiment and the items described in the "Means for Solving the Problems" column are as follows. The crank side acquisition process corresponds to the processes of S40 and S42. The latter-stage acquisition process corresponds to the process of S44. The torsional velocity component calculation process corresponds to the processes of S48 to S58. The stiffness value varying process corresponds to the processes of S50 to S54. The variation amount calculation process for determination corresponds to the process of S16. The determination process corresponds to the process of S18.

<Other embodiments>
In addition, this embodiment can be changed and implemented as follows. This embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

"About crank-side speed variables"
In the above embodiment, the crank angle range defining the crank-side speed variable, which is the variable indicating the rotation speed of the crankshaft 12 in the crank angle range below the interval between compression top dead centers, is set to 30° CA. Not exclusively. For example, it may be 10° CA, or, for example, the interval itself between compression top dead centers.

- The crank-side speed variable is not limited to the quantity having the dimension of time, and may be the quantity having the dimension of speed, for example.
"Regarding the Rotation Fluctuation"
In the above-described embodiment, the rotation fluctuation amount ΔT30 is the difference between the crank-side speed variables separated by 120° CA, but it is not limited to this. For example, it may be a difference between crank-side speed variables separated by 90° CA.

- The rotation fluctuation amount is not limited to the difference between the crank-side speed variables, and may be the ratio between the crank-side speed variables.
"Regarding provisional judgment processing"
The provisional determination process is not limited to using the difference between the rotational fluctuation amounts ΔT30 that are separated from each other by 360° CA or 720° CA. In short, by using the difference between the rotation fluctuation amounts ΔT30 separated by integral multiples of 360° CA, it is possible to prevent the accuracy of the provisional determination from deteriorating due to the tolerance of the tooth portion 22 of the crank rotor 20 .

The provisional determination process is not limited to comparing the difference between the rotation fluctuation amounts ΔT30 separated from each other by an integer multiple of 360° CA with the threshold value, but the rotation fluctuation amount of the cylinder to be judged and the threshold value. A process of directly comparing sizes may be used.

"About vehicle"
・The hybrid vehicle is not limited to a series/parallel hybrid vehicle. For example, it may be a parallel hybrid vehicle. However, the vehicle is not limited to a hybrid vehicle, and may be a vehicle in which the internal combustion engine 10 is the only thrust generating device of the vehicle.

DESCRIPTION OF SYMBOLS 10... Internal combustion engine 12... Crankshaft 14... Damper 14a... Coil spring 14b... Seat 20... Crank rotor 30... Planetary gear mechanism 34... Drive wheel

Claims (1)

Applied to internal combustion engines with multiple cylinders,
The crankshaft of the internal combustion engine is connected to a torsionally rigid body,
executing crank-side acquisition processing, post-stage acquisition processing, torsional velocity component calculation processing, determination variation amount calculation processing, and determination processing;
The crank-side acquisition process is a process of acquiring a crank-side speed variable, which is a variable indicating the rotation speed of the crankshaft, based on the crank signal,
The latter-stage acquisition process is a process of acquiring a latter-stage speed variable, which is a variable indicating a rotational speed of the torsionally rigid body on the opposite side of the crankshaft,
The torsional velocity component calculation process is a process of inputting the difference between the crank-side velocity variable and the rear-stage-side velocity variable and calculating the torsional velocity component, which is the velocity component caused by the torsion of the torsional rigid body, based on the damper stiffness value. which includes a stiffness value variable process,
The determination variation amount calculation process is a process of calculating a determination variation amount based on the value of the crank-side speed variable from which the torsional speed component has been removed,
The determination variation amount is an amount indicating a rotation variation amount used for misfire determination,
The rotation fluctuation amount is the amount of change in the crank-side speed variable,
The determination process is a process for determining whether or not there is a misfire in the internal combustion engine based on the magnitude of the variation amount for determination,
The misfire detection device for an internal combustion engine, wherein the stiffness value varying process is a process of changing the damper stiffness value based on the magnitude of the load on the internal combustion engine.

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